At present, a non-power four-wheeled trolley is widely used on various occasions. For example, sick bed, handcart used in a supermarket, baby cart, conveying trolley, etc. all are very useful implements. However, some accidents often occur when using these trolleys. For instance, such a trolley often slips away unexpectedly due to inclination of the ground so as to collide with persons or obstacles or even a car on a road. A braking mechanism for the trolley can be applied to stop the trolley. However, prior braking mechanism can only brake two of the four wheels of the trolley, while the other two can still rotate to make the trolley circle about the braked wheels.
Moreover, no wheel-orienting mechanism is provided for the conventional trolleys or only two of the four wheels are provided with the wheel-orienting mechanism. Therefore, when the trolley is moved upward on an inclination, a user must exert more force on the trolley to prevent the trolley from displacing laterally.